Dan's work pushed the adoption of BCP38, segmentation of authoritative and recursive resolvers, and better source port randomization. Entirely new mitigations were developed like 0x20, source address randomization, and double response detection.

Additional mitigations started to come in to play after that to make it both impractical, detectable, and improbable. It's just shy of impossible now, and in the very unusual scenarios where it's possible, it's so easily detectable.